I advise against the oil additive for now. You are not sure where the leak is from.
Have you tried tightening the oil pan bolts? 106 in/lbs is easily achieved by hand, even in a tight location.
Though oil is collecting at the oil pan gasket, that area may not be the source of the leak. The oil leak could be originating at a higher point.
Good luck and let us know how it goes.

I agree not to use additives. They containe chemicals that swell all the seals not just the leaking ones. If it's the front seal or loose pan bolts it is possible to fix whit out pulling motor. Good luck.